EP3308883A1

EP3308883A1 - Porous copper body, porous copper composite member, method for producing porous copper body, and method for producing porous copper composite member

Info

Publication number: EP3308883A1
Application number: EP16807273.4A
Authority: EP
Inventors: Koichi Kita; Jun Kato; Toshihiko Saiwai
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2015-06-12
Filing date: 2016-05-23
Publication date: 2018-04-18
Also published as: US10493528B2; CN107530776A; KR20180016985A; WO2016199566A1; JP6107888B2; EP3308883A4; US20180161877A1; CN107530776B; JP2017002375A

Abstract

A porous copper body (10, 110) including a skeleton (12) having a three-dimensional network structure is provided. An oxidation-reduction layer formed by an oxidation-reduction treatment is provided on a surface of the skeleton (12), and the oxygen concentration of the entirety of the skeleton (12) is set to be 0.025 mass% or less.

Description

TECHNICAL FIELD

The present invention relates to a porous copper body made of copper or a copper alloy, a porous copper composite part in which the porous copper body is bonded to a main body of the composite part, a method for manufacturing the porous copper body, and a method for manufacturing the porous copper composite part.
Priority is claimed on Japanese Patent Application No. 2015-119523, filed on June 12, 2015 , the content of which is incorporated herein by reference.

BACKGROUND ART

The above-mentioned porous copper body and the porous copper composite part are used, for example, as electrodes and current collectors in various batteries, heat exchanger components, silencing components, filters, impact-absorbing components, and the like.
For example, PTL 1 discloses a heat transfer member having a three-dimensional network structure which is obtained by sintering a powder made of copper or a copper alloy as a raw material in a reduction atmosphere.
PTL 2 discloses a heat exchange member in which a porous copper layer is formed on a surface of a copper tube by sintering a copper powder.

CITATION LIST

PATENT LITERATURE

PTL 1: Japanese Unexamined Patent Application, First Publication No. H08-145592
PTL 2: Japanese Unexamined Patent Application, First Publication No. H11-217680

SUMMARY OF INVENTION

TECHNICAL PROBLEM

In PTL 1, sintering is performed in an inert gas atmosphere or a reduction atmosphere. In PTL 2, a powder made of copper or a copper alloy is used as a raw material, and the raw material powder is temporarily bonded to a surface of a copper tube using a binder, followed by an oxidation treatment and a reduction treatment to sinter the copper raw material and form a porous copper layer. As described in PTL 1 and PTL 2, when performing only sintering in an inert gas atmosphere or a reduction atmosphere, a metal bond of copper is insufficient, and there is a concern that thermal conductivity or electrical conductivity may be insufficient.
The present invention has been made in consideration of the above-described circumstances, and an objective thereof is to provide a porous copper body in which copper raw materials are sufficiently bonded to each other and which is particularly excellent in thermal conductivity and electrical conductivity, a porous copper composite part in which the porous copper body is bonded to a main body of the composite part, a method for manufacturing the porous copper body, and method for manufacturing the porous copper composite part.

SOLUTION TO PROBLEM

To solve the above-described problem and to accomplish the above-described objective, a porous copper body according to an aspect of the present invention (hereinafter, referred to as "porous copper body of the present invention") includes a skeleton having a three-dimensional network structure, in which an oxidation-reduction layer formed by an oxidation-reduction treatment is provided on a surface of the skeleton, and an oxygen concentration of an entirety of the skeleton is set to be 0.025 mass% or less.
According to the porous copper body having such configuration, since the porous copper body includes the oxidation-reduction layer formed by the oxidation-reduction treatment on the surface of the skeleton, a specific surface area increases. Therefore, for example, it is possible to greatly improve heat exchange efficiency and the like.
Since the oxygen concentration of the entirety of the skeleton is set to be 0.025 mass% or less, copper raw materials are sufficiently metal-bonded through the oxidation-reduction treatment, and thus thermal conductivity and electrical conductivity are particularly excellent.
In the porous copper body of the present invention, it is preferable that a specific surface area of an entirety of the porous copper body be set to be 0.01 m²/g or greater, and a porosity of the entirety of the porous copper body be set to be in a range of 50% to 90%.
In this case, the specific surface area is set to be great, and the porosity is set to be high. Therefore, for example, it is possible to surely improve heat exchange efficiency and the like.
In the porous copper body of the present invention, it is preferable that the skeleton be constituted by a sintered body made of a plurality of copper fibers, and in each of the copper fibers, a diameter R be set to be in a range of 0.02 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R be set to be in a range of 4 to 2500.
In this case, the copper fibers in which the diameter R is set to be in a range of 0.02 mm to 1.0 mm, and the ratio L/R of the length L to the diameter R is set to be in a range of 4 to 2500, are sintered. Therefore, voids are sufficiently retained between the copper fibers, and a shrinkage ratio in the sintering can be limited. Accordingly, it is possible to raise the porosity, and the dimensional accuracy is excellent.
A porous copper composite part according to another aspect of the present invention (hereinafter, referred to as "porous copper composite part of the present invention") includes: a main body of the composite part; and the above-described porous copper body bonded to the main body of the composite part.
According to the porous copper composite part having such configuration, the porous copper body having excellent stability of surface properties is strongly bonded to the main body of the composite part. Therefore, as the porous copper composite part, excellent thermal conductivity and excellent electrical conductivity can be exhibited.
In the porous copper composite part of the present invention, it is preferable that a bonding surface of the main body of the composite part, to which the porous copper body is bonded, be made of copper or a copper alloy, and the porous copper body and the main body of the composite part be bonded to each other through sintering.
In this case, the porous copper body and the main body of the composite part are integrally bonded to each other through the sintering, and thus the porous copper body and the main body of the composite part are strongly bonded to each other. Therefore, as the porous copper composite part, excellent thermal conductivity and excellent electrical conductivity are exhibited.
A method for manufacturing a porous copper body according to still another aspect of the present invention (hereinafter, referred to as "method for manufacturing a porous copper body of the present invention") is a method for manufacturing the above-described porous copper body which includes: a skeleton forming step of forming the skeleton having the oxygen concentration of 0.025 mass% or less; and an oxidation-reduction step of forming the oxidation-reduction layer on the surface of the skeleton.
According to the method for manufacturing the porous copper body having such configuration, the method includes: the skeleton forming step of forming the skeleton having an oxygen concentration of 0.025 mass% or less; and the oxidation-reduction step of forming the oxidation-reduction layer on the surface of the skeleton. Therefore, it is possible to obtain a porous copper body in which a specific surface area increases, copper raw materials are sufficiently metal-bonded through the oxidation-reduction treatment, and thermal conductivity and electrical conductivity are particularly excellent.
The method for manufacturing the porous copper body of the present invention may further include: a copper raw material lamination step of laminating a copper raw material having an oxygen concentration of 0.03 mass% or less; and a sintering step of sintering a plurality of the copper raw materials which are laminated. In the sintering step, the copper fibers may be oxidized and then the oxidized copper fibers may be reduced, thereby bonding the copper fibers to each other so as to form the skeleton and forming the oxidation-reduction layer on the surface of the skeleton. That is, in the method for manufacturing the porous copper body, the above-described skeleton forming step and the oxidation-reduction step are performed in the copper raw material lamination step and the sintering step.
In this case, the copper raw materials having an oxygen concentration of 0.03 mass% or less are used, and thus it is possible to set an oxygen concentration in the porous copper body after sintering to be 0.025 mass% or less. In the sintering step, the copper fibers are oxidized, and then the oxidized copper fibers are reduced and are bonded to each other, and thus it is possible to form the oxidation-reduction layer on the surface of the skeleton.
The method for manufacturing the porous copper body of the present invention may further include a preliminary reduction treatment of decreasing the oxygen concentration of the copper raw materials.
In this case, since the method includes the preliminary reduction treatment of decreasing the oxygen concentration of the copper raw materials, it is possible to limit the oxygen concentration of the copper raw materials to 0.03 mass% or less, and it is possible to set the oxygen concentration in the porous copper body after sintering to be 0.025 mass% or less.
A method for manufacturing a porous copper composite part according to still another aspect of the present invention (hereinafter, referred to as "method for manufacturing a porous copper composite part of the present invention") is a method for manufacturing a porous copper composite part in which includes: a main body of the composite part; and a porous copper body bonded to the main body of the composite part. The method includes a bonding step of bonding the porous copper body manufactured by the above-described method for manufacturing the porous copper body, and the main body of the composite part to each other.
According to the method for manufacturing a porous copper composite part having such configuration, the porous copper body manufactured by the above-described method for manufacturing the porous copper body is provided, and thus it is possible to manufacture a porous copper composite part having excellent thermal conductivity and electrical conductivity.
In the method for manufacturing a porous copper composite part of the present invention, it is preferable that, a bonding surface of the main body of the composite part, to which the porous copper body is bonded, be made of copper or a copper alloy, and the porous copper body and the main body of the composite part be bonded to each other through sintering.
In this case, the main body of the composite part and the porous copper body can be integrated with each other through the sintering, and thus it is possible to manufacture a porous copper composite part having excellent thermal conductivity and electrical conductivity.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a porous copper body in which copper raw materials are sufficiently bonded to each other and which is particularly excellent in thermal conductivity and electrical conductivity, a porous copper composite part in which the porous copper body is bonded to a main body of the composite part, a method for manufacturing the porous copper body, and method for manufacturing the porous copper composite part.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an enlarged schematic view of a porous copper body according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing an example of a method for manufacturing the porous copper body shown in FIG. 1.
FIG. 3 is a view showing a manufacturing process of manufacturing the porous copper body shown in FIG. 1.
FIG. 4 is a view showing an external appearance of a porous copper composite part according to a second embodiment of the present invention.
FIG. 5 is a flowchart showing an example of a method for manufacturing the porous copper composite part shown in FIG. 4.
FIG. 6 is an external view of a porous copper composite part according to another embodiment of the present invention.
FIG. 7 is an external view of a porous copper composite part according to still another embodiment of the present invention.
FIG. 8 is an external view of a porous copper composite part according to still another embodiment of the present invention.
FIG. 9 is an external view of a porous copper composite part according to still another embodiment of the present invention.
FIG. 10 is an external view of a porous copper composite part according to still another embodiment of the present invention.
FIG. 11 is an external view of a porous copper composite part according to still another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a porous copper body, a porous copper composite part, a method for manufacturing the porous copper body, and a method for manufacturing the porous copper composite part according to embodiments of the present invention will be described with reference to the accompanying drawings.

(First Embodiment)

First, a porous copper body 10 according to a first embodiment of the present invention will be described with reference to FIG. 1 to FIG. 3.
As shown in FIG. 1, the porous copper body 10 according to this embodiment includes a skeleton 12 formed by sintering a plurality of copper fibers 11.
Each of the copper fibers 11 is made of copper or a copper alloy. In this embodiment, for example, each of the copper fibers 11 is made of C1100 (tough pitch copper). In the copper fiber 11, a diameter R is set to be in a range of 0.02 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R is set to be in a range of 4 to 2500.
In this embodiment, the copper fibers 11 are subjected to shape imparting such as twisting and bending.
In the porous copper body 10 according to this embodiment, an apparent density D_A is set to be 51 % or less of a true density D_T of the copper fibers 11. The shape of each copper fiber 11 is an arbitrary shape, such as a linear shape and a curved shape, as long as the apparent density D_A is 51% or less of the true density D_T of the copper fibers 11. However, when using the copper fibers 11 in which at least a part thereof is subjected to a processing for imparting a predetermined shape such as twisting and bending, it is possible to form voids between fibers in a three-dimensional and isotropic shape. As a result, it is possible to improve the isotropy of various properties such as the heat transfer properties and the electrical conductivity of the porous copper body 10.
The copper fibers 11 are manufactured through adjustment into a predetermined equivalent circle diameter by a drawing method, a coil cutting method, a wire cutting method, a melt-spinning method and the like, length adjustment for satisfying predetermined L/R, and cutting.
The equivalent circle diameter R is a value calculated on the basis of a cross-sectional area A of each fiber, and is defined by the following expression on the assumption of a true circle regardless of a cross-sectional shape. $R = {(A / π)}^{1 / 2} \times 2$
In the porous copper body 10 according to this embodiment, an oxidation-reduction layer is formed on a surface of the skeleton 12 (copper fibers 11). In bonding portions between the copper fibers 11, oxidation-reduction layers formed on surfaces of the copper fibers 11 are integrally bonded to each other.
Each of the oxidation-reduction layers has a porous structure, and causes minute unevenness on the surface of skeleton 12 (copper fibers 11). According to this, a specific surface area of the entirety of the porous copper body 10 is set to be 0.01 m²/g or greater, and a porosity thereof is set to be in a range of 50% to 90%.
Although not particularly limited, the upper limit of the specific surface area of the entirety of the porous copper body 10 is 0.50 m²/g.
Although not particularly limited, a range of the specific surface area of the entirety of the porous copper body 10 is preferably 0.03 m²/g to 0.40 m²/g, and more preferably 0.05 m²/g to 0.30 m²/g. Similarly, although not particularly limited, a range of the porosity is 60% to 90%, and more preferably 70% to 90%.
In the porous copper body 10 according to this embodiment, an oxygen concentration of the entirety of the skeleton 12 is set to be 0.025 mass% or less.
The lower limit of the oxygen concentration of the entirety of the skeleton 12 is a value depending on a grade of copper used, and is not particularly limited. The lower limit of the oxygen concentration in a case of using oxygen-free copper is approximately 0.00001 mass%.
Next, a method for manufacturing the porous copper body 10 according to this embodiment will be described with reference to a flowchart in FIG. 2, a process diagram of FIG. 3, and the like.
First, copper fibers 11 having the oxygen concentration of 0.03 mass% or less are prepared. In this embodiment, for example, a preliminary reduction treatment step S00 is performed on copper fibers 11 having an oxygen concentration of approximately 0.05 mass%, and thereby the oxygen concentration of the copper fibers 11 is decreased to 0.03 mass% or less. By this preliminary reduction treatment step S00, an oxygen amount, particularly, on the surfaces of the copper fibers 11, is decreased. Even in a case where the oxygen concentration of the copper fibers 11 is 0.03 mass% or less before performing the preliminary reduction treatment step S00, by performing the preliminary reduction treatment step S00, it is possible to increase the cleanness of the surfaces of the copper fibers 11.
In this embodiment, conditions of the preliminary reduction treatment step S00 are set such that the atmosphere is a mixed gas atmosphere of argon and hydrogen, the holding temperature is in a range of 350°C to 850°C, and the holding temperature is in a range of 5 minutes to 120 minutes.
In a case where the holding temperature in the preliminary reduction treatment step S00 is lower than 350°C, there is a concern that the copper fibers 11 cannot be sufficiently reduced and thus the oxygen concentration of the copper fibers 11 cannot be decreased. On the other hand, in a case where the holding temperature in the preliminary reduction treatment step S00 is higher than 850°C, there is a concern that the copper fibers 11 may be sintered with each other in the preliminary reduction treatment step S00.
From the above, in this embodiment, the holding temperature in the preliminary reduction treatment step S00 is set to be 350°C to 850°C. It is preferable to set the lower limit of the holding temperature in the preliminary reduction treatment step S00 to be 400°C or higher in order to sufficiently decrease the oxygen concentration of the copper fibers 11. It is preferable that the upper limit of the holding temperature be 800°C or lower in order to surely suppress sintering of the copper fibers 11 in the preliminary reduction treatment step S00.
In a case where the holding time in the preliminary reduction treatment step S00 is shorter than 5 minutes, there is a concern that the copper fibers 11 cannot be sufficiently reduced and thus the oxygen concentration cannot be decreased. On the other hand, in a case where the holding time in the preliminary reduction treatment step S00 is longer than 120 minutes, there is a concern that the copper fibers 11 may be sintered with each other in the preliminary reduction treatment step S00.
From the above, in this embodiment, the holding time in the preliminary reduction treatment step S00 is set to be in a range of 5 minutes to 120 minutes. It is preferable that the lower limit of the holding time in the preliminary reduction treatment step S00 be set to be 10 minutes or longer in order to sufficiently decrease the oxygen concentration of the copper fiber 11. It is preferable that the upper limit of the holding time be set to be 100 minutes or shorter in order to surely suppress sintering of the copper fibers 11 in the preliminary reduction treatment step S00.
Next, as shown in FIG. 3, the copper fibers 11 after the preliminary reduction treatment step S00 are distributed from a distributor 31 toward the inside of a stainless-steel container 32 to bulk-fill the stainless-steel container 32. Thereby, the copper fibers 11 are laminated (copper fibers lamination step S01).
In the copper fibers lamination step S01, a plurality of the copper fibers 11 are laminated so that a bulk density D_P after the filling becomes 50% or less of the true density D_T of the copper fibers 11. In this embodiment, the copper fibers 11 are subjected to a processing for imparting a shape such as twisting and bending, and thus it is possible to retain three-dimensional and isotropic voids between the copper fibers 11 during lamination.
Next, the copper fibers 11 bulk-filling the stainless-steel container 32 are subjected to an oxidation-reduction treatment (oxidation-reduction treatment step S02).
As shown in FIG. 2 and FIG. 3, the oxidation-reduction treatment step S02 includes: an oxidation treatment step S21 of performing an oxidation treatment on the copper fibers 11, and a reduction treatment step S22 of reducing and sintering the copper fibers 11 subjected to the oxidation treatment.
In this embodiment, as shown in FIG. 3, the stainless-steel container 32 filled with the copper fibers 11 is put in a heating furnace 33 and heated in an air atmosphere to perform an oxidation treatment on the copper fibers 11 (oxidation treatment step S21). Through the oxidation treatment step S21, an oxide layer, for example, with a thickness of 1 µm to 100 µm is formed on a surface of each of the copper fibers 11.
Conditions of the oxidation treatment step S21 in this embodiment are set such that the holding temperature is in a range of 520°C to 1050°C and the holding time is in a range of 5 minutes to 300 minutes.
In a case where the holding temperature in the oxidation treatment step S21 is lower than 520°C, there is a concern that the oxide layers are not sufficiently formed on the surfaces of the copper fibers 11. On the other hand, in a case where the holding temperature in the oxidation treatment step S21 is higher than 1050°C, there is a concern that oxidation may progress to the inside of the copper fibers 11.
From the above, in this embodiment, the holding temperature in the oxidation treatment step S21 is set to be 520°C to 1050°C. In the oxidation treatment step S21, it is preferable that the lower limit of the holding temperature be set to be 600°C or higher, and the upper limit of the holding temperature be set to be 1000°C or lower in order to surely form the oxide layers on the surfaces of the copper fibers 11.
In a case where the holding time in the oxidation treatment step S21 is shorter than 5 minutes, there is a concern that the oxide layers may not be sufficiently formed on the surfaces of the copper fibers 11. On the other hand, in a case where the holding time in the oxidation treatment step S21 is longer than 300 minutes, there is a concern that oxidation may progress to the inside of the copper fibers 11.
From the above, in this embodiment, the holding time in the oxidation treatment step S21 is set to be in a range of 5 minutes to 300 minutes. It is preferable that the lower limit of the holding time in the oxidation treatment step S21 be set to be 10 minutes or longer in order to surely form the oxide layers on the surfaces of the copper fibers 11. It is preferable that the upper limit of the holding time in the oxidation treatment step S21 be set to be 100 minutes or shorter in order to surely suppress oxidation on the inside of the copper fibers 11.
In this embodiment, as shown in FIG. 3, after performing the oxidation treatment step S21, the stainless steel container 32 filled with the copper fibers 11 is put in the heating furnace 34 and is heated in a reduction atmosphere. According to this, the oxidized copper fibers 11 are subjected to a reduction treatment to form an oxidation-reduction layer, and the copper fibers 11 are bonded to each other to form the skeleton 12 (reduction treatment step S22).
Conditions of the reduction treatment step S22 in this embodiment are set such that the atmosphere is a mixed gas atmosphere of argon and hydrogen, the holding temperature is in a range of 600°C to 1080°C, and the holding time is in a range of 5 minutes to 300 minutes.
In a case where the holding temperature in the reduction treatment step S22 is lower than 600°C, there is a concern that the oxide layers formed on the surfaces of the copper fibers 11 may not be sufficiently reduced. On the other hand, in a case where the holding temperature in the reduction treatment step S22 is higher than 1080°C, the copper fibers are heated to near the melting point of copper, and thus there is a concern that strength and porosity may decrease.
From the above, in this embodiment, the holding temperature in the reduction treatment step S22 is set to be 600°C to 1080°C. It is preferable that the lower limit of the holding temperature in the reduction treatment step S22 be set to be 650°C or higher in order to surely reduce the oxide layers formed on the surfaces of the copper fibers 11. It is preferable that the upper limit of the holding temperature in the reduction treatment step S22 be set to be 1050°C or lower in order to surely limit a decrease in strength and the porosity.
In a case where the holding time in the reduction treatment step S22 is shorter than 5 minutes, there is a concern that the oxide layers formed on the surfaces of the copper fibers 11 may not be sufficiently reduced and sintering may become insufficient. On the other hand, in a case where the holding time in the reduction treatment step S22 is longer than 300 minutes, there is a concern that thermal shrinkage due to the sintering may increase and strength may decrease.
From the above, in this embodiment, the holding time in the reduction treatment step S22 is set to be in a range of 5 minutes to 300 minutes. It is preferable that the lower limit of the holding temperature in the reduction treatment step S22 be set to be 10 minutes or longer in order to surely reduce the oxide layers formed on the surfaces of the copper fibers 11 and to allow sintering to sufficiently progress. It is preferable that the upper limit of the holding time in the reduction treatment step S22 be set to be 100 minutes or shorter in order to surely limit thermal shrinkage due to the sintering or a decrease in strength.
An oxidation-reduction layer is formed on the surface of the copper fibers 11 (skeleton 12) by the oxidation treatment step S21 and the reduction treatment step S22 and thus minute unevenness is formed.
The oxide layers are formed on the surfaces of the copper fibers 11 by the oxidation treatment step S21, and a plurality of the copper fibers 11 are cross-linked through the oxide layers. Then, by performing the reduction treatment step S22, the oxide layers formed on the surfaces of the copper fibers 11 are reduced so as to form the above-described oxidation-reduction layers. In addition, the oxidation-reduction layers are bonded to each other and thereby the copper fibers 11 are sintered so as to form the skeleton 12.
According to the manufacturing method as described above, the copper fibers 11 are sintered so as to form the skeleton 12, and the oxidation-reduction layer is formed on the surface of the skeleton 12 (copper fibers 11). The oxygen concentration of the entirety of the skeleton 12 is set to be 0.025 mass% or less, and thus the porous copper body 10 according to this embodiment is manufactured.
According to the porous copper body 10 of this embodiment described above, since the oxygen concentration of the entirety of the skeleton 12 is set to be 0.025 mass% or less, the copper fibers 11 are surely metal-bonded by the oxidation treatment step S21 and the reduction treatment step S22, and thus the thermal conductivity and the electrical conductivity are particularly excellent.
In a case where the oxygen concentration of the entirety of the skeleton 12 is greater than 0.025 mass%, there is a concern that the metal bonding of the copper fibers 11 may become insufficient and thus the thermal conductivity and the electrical conductivity may deteriorate.
From the above, in this embodiment, the oxygen concentration of the entirety of the skeleton 12 is set to be 0.25 mass% or less. It is preferable that the oxygen concentration of the entirety of the skeleton 12 be set to be 0.02 mass% or less in order to further improve the thermal conductivity and electrical conductivity.
In the porous copper body 10 according to this embodiment, the skeleton 12 is formed by sintering the copper fibers 11 in which the diameter R is set to be in a range of 0.02 mm to 1.0 mm, and the ratio L/R of the length L to the diameter R is set to be in a range of 4 to 2500. Therefore, voids are sufficiently retained between the copper fibers 11, and it is possible to limit the shrinkage ratio in the sintering. As a result, the porosity is high and the dimensional accuracy is excellent.
This embodiment includes the copper fibers lamination step S01 in which the copper fibers 11 having the diameter R in a range of 0.02 mm to 1.0 mm and the ratio L/R of the length L to the diameter R in a range of 4 to 2500 are laminated so that the bulk density D_P is 50% or less of the true density D_T of the copper fibers 11. Therefore, it is possible to retain voids between the copper fibers 11 and limit shrinkage. According to this, it is possible to manufacture the porous copper body 10 having high porosity and excellent dimensional accuracy.
Specifically, the apparent density D_A of the porous copper body 10 which is manufactured by sintering the copper fibers 11 laminated so that the bulk density D_P is 50% or less of the true density D_T of the copper fibers 11, is set to be 51 % or less of the true density D_T of the copper fibers 11. Therefore, shrinkage during the sintering is limited, and thus a high porosity can be retained.
In a case where the diameter R of the copper fibers 11 is less than 0.02 mm, there is a concern that a bonding area between the copper fibers 11 may be small and thus sintering strength may be deficient. On the other hand, in a case where the diameter R of the copper fibers 11 is greater than 1.0 mm, there is a concern that the number of contact points at which the copper fibers 11 come into contact with each other may be deficient and thus the sintering strength may be deficient.
From the above, in this embodiment, the diameter R of the copper fibers 11 is set to be in a range of 0.02 mm to 1.0 mm. It is preferable that the lower limit of the diameter R of the copper fibers 11 be set to be 0.05 mm or greater, and the upper limit of the diameter R of the copper fibers 11 be set to be 0.5 mm or less in order to further improve strength.
In a case where the ratio L/R of the length L to the diameter R of the copper fibers 11 is less than 4, it is difficult for the bulk density D_P to be 50% or less of the true density D_T of the copper fibers 11 when laminating the copper fibers 11, and thus there is a concern that it is difficult to obtain the porous copper body 10 with a high porosity. On the other hand, in a case where the ratio L/R of the length L to the diameter R of the copper fibers 11 is greater than 2500, there is a concern that the copper fibers 11 cannot be uniformly dispersed and thus it is difficult to obtain the porous copper body 10 with a uniform porosity.
From the above, in this embodiment, the ratio L/R of the length L to the diameter R of the copper fibers 11 is set to be in a range of 4 to 2500. It is preferable that the lower limit of the ratio L/R of the length L to the diameter R of the copper fibers 11 be set to be 10 or greater in order to further improve porosity. It is preferable that the upper limit of the ratio L/R of the length L to the diameter R of the copper fibers 11 be set to be 500 or less in order to surely obtain the porous copper body 10 with a uniform porosity.
The method for manufacturing the porous copper body according to this embodiment includes: the oxidation treatment step S21 of oxidizing the copper fibers 11; and the reduction treatment step S22 of reducing the oxidized copper fibers 11. Therefore, it is possible to form the oxidation-reduction layer on the surface of the copper fibers 11 (skeleton 12).
In the method for manufacturing the porous copper body according to this embodiment, the copper fibers 11 of which the oxygen concentration is set to be 0.03 mass% or less by the preliminary reduction treatment step S00, are used. Thus, it is possible to set the oxygen concentration of the entirety of the skeleton 12 to be 0.025 mass% or less.

(Second Embodiment)

A porous copper composite part 100 according to a second embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 4 shows the porous copper composite part 100 according to this embodiment. The porous copper composite part 100 includes: a copper plate 120 (main body of the composite part) made of copper or a copper alloy; and a porous copper body 110 bonded to the surface of the copper plate 120.
In the porous copper body 110 according to this embodiment, a plurality of copper fibers are sintered to form a skeleton in the same manner as in the first embodiment. The copper fibers are made of copper or a copper alloy, and have a diameter R set to be in a range of 0.02 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R set to be in a range of 4 to 2500. In this embodiment, the copper fibers are made of, for example, oxygen-free copper.
In this embodiment, the copper fibers are subjected to shape imparting such as twisting and bending. In the porous copper body 110 according to this embodiment, an apparent density D_A thereof is set to be 51% or less of a true density D_T of the copper fibers.
In this embodiment, by performing an oxidation-reduction treatment (an oxidation treatment and a reduction treatment) as described later, an oxidation-reduction layers are formed on the surfaces of the copper fibers (skeleton) constituting the porous copper body 110 and the copper plate 120. Thereby, minute unevenness is formed on the surfaces of copper fibers (skeleton) and the copper plate 120. In this embodiment, a specific surface area of the entirety of the porous copper body 110 is set to be 0.01 m²/g or greater, and the porosity thereof is set to be in a range of 50% to 90%.
An oxidation-reduction layer formed on the surface of the copper fibers and an oxidation-reduction layer formed on the surface of the copper plate 120 are integrally bonded to each other at bonding portions between the surfaces of the copper fibers constituting the porous copper body 110 and the copper plate 120.
In this embodiment, the oxygen concentration of the entirety of the skeleton of the porous copper body 110 is set to be 0.025 mass% or less.
The lower limit of the oxygen concentration of the entirety of the skeleton 12 is a value depending on a grade of copper used, and is not particularly limited. In a case where the oxygen-free copper is used, the lower limit of the oxygen concentration is approximately 0.00001 mass%.
Next, a method for manufacturing the porous copper composite part 100 according to this embodiment will be described with reference to a flowchart in FIG. 5.
First, the copper plate 120 as a main body of the composite part is prepared (copper plate-disposing step S100). Copper fibers with an oxygen concentration of 0.03 mass% or less are dispersed and laminated on the surface of the copper plate 120 (copper fibers lamination step S101). In the copper fibers lamination step S101, a copper fiber with an oxygen concentration of 0.03 mass% or less is used, and a plurality of the copper fibers are laminated so that a bulk density D_P is 50% or less of a true density D_T of the copper fibers.
Next, the copper fibers laminated on the surface of the copper plate 120 are sintered to shape the porous copper body 110 and to bond the porous copper body 110 and the copper plate 120 to each other (a sintering step S102 and a bonding step S103). As shown in FIG. 5, the sintering step S102 and the bonding step S103 include: an oxidation treatment step S121 of performing an oxidation treatment of the copper fibers and the copper plate 120; and a reduction treatment step S122 of reducing and sintering the copper fibers and the copper plate 120 having subjected to the oxidization treatment.
In this embodiment, the copper plate 120 on which the copper fibers are laminated is put in a heating furnace, and is heated in an air atmosphere to perform an oxidization treatment on the copper fibers (oxidation treatment step S121). According to the oxidation treatment step S121, for example, oxide layers with a thickness of 1 µm to 100 µm are formed on the surfaces of the copper fibers and the copper plate 120.
Conditions of the oxidation treatment step S121 in this embodiment are set such that the holding temperature is in a range of 520°C to 1050°C and preferably 600°C to 1000°C, and the holding time is in a range of 5 minutes to 300 minutes and preferably 10 minutes to 100 minutes.
In this embodiment, after performing the oxidation treatment step S121, the copper plate 120 on which the copper fibers are laminated is put in a sintering furnace, and is heated in a reduction atmosphere to perform a reduction treatment on the oxidized copper fibers and the oxidized copper plate 120. Thereby, the copper fibers are bonded to each other and the copper fibers and the copper plate 120 are bonded to each other (reduction treatment step S122).
Conditions of the reduction treatment step S122 in this embodiment are set such that the atmosphere is a mixed gas atmosphere of nitrogen and hydrogen, the holding temperature is in a range of 600°C to 1080°C and preferably 650°C to 1050°C, and the holding time is in a range of 5 minutes to 300 minutes and preferably 10 minutes to 100 minutes.
By the oxidation treatment step S121 and the reduction treatment step S122, an oxidation-reduction layer is formed on the surfaces of the copper fibers (skeleton) and the copper plate 120 and minute unevenness is formed.
Oxide layers are formed on the surfaces of the copper fibers (skeleton) and the copper plate 120 by the oxidation treatment step S121. Through the oxide layers, a plurality of the copper fibers are cross-linked to each other and to the copper plate 120. Then, by performing the reduction treatment S122, the oxide layers formed on the surfaces of the copper fibers (skeleton) and the copper plate 120 are reduced. Thereby, the copper fibers are sintered through the oxidation-reduction layer to form the skeleton and the porous copper body 110 and the copper plate 120 are bonded to each other.
According to the manufacturing method as described above, the porous copper composite part 100 according to this embodiment is manufactured.
According to the porous copper composite part 100 of this embodiment described above, since the oxygen concentration of the entirety of the skeleton of the porous copper body 110 is set to be 0.025 mass% or less, the copper fibers 11 are surely metal-bonded to each other by the oxidation treatment step S121 and the reduction treatment step S122, and the thermal conductivity and the electrical conductivity are particularly excellent.
In the porous copper composite part 100 according to this embodiment, the porous copper body 110 is obtained through sintering of the copper fibers having the diameter R set to be in a range of 0.02 mm to 1.0 mm and the ratio L/R of the length L to the diameter R set to be in a range of 4 to 2500, and thus has a high porosity and excellent strength and dimensional accuracy. This porous copper body 110 is bonded to the surface of the copper plate 120. Therefore, various properties thereof, such as the heat transfer properties and the electrical conductivity, are excellent.
In this embodiment, the oxidation-reduction layer is formed on the surfaces of the copper fibers constituting the porous copper body 110 and the copper plate 120, the specific surface area of the entirety of the porous copper body 110 is set to be 0.01 m²/g or greater, and the porosity thereof is set to be in a range of 50% to 90%. Therefore, it is possible to greatly improve heat exchange efficiency and the like.
Although not particularly limited, the upper limit of the specific surface area of the entirety of the porous copper body 10 is 0.50 m²/g.
Although not particularly limited, the specific surface area of the entirety of the porous copper body 10 is preferably 0.03 m²/g to 0.40 m²/g and more preferably 0.05 m²/g to 0.30 m²/g. Similarly, although not particularly limited, the porosity is preferably 60% to 90%, and more preferably 70% to 90%.
In this embodiment, an oxidation-reduction layer formed on the surface of the copper fibers and an oxidation-reduction layer formed on the surface of the copper plate 120 are integrally bonded to each other at bonding portions between the surfaces of the copper fibers constituting the porous copper body 110 and the copper plate 120. Therefore, the porous copper body 110 and the copper plate 120 are strongly bonded to each other, and thus various properties thereof, such as the strength of a bonding interface, the heat transfer properties, and the electrical conductivity are excellent.
According to the method for manufacturing the porous copper composite part 100 of this embodiment, the oxygen-free copper with an oxygen concentration of 0.03 mass% or less is used as the copper fibers, and thus the oxygen concentration of the entirety of the skeleton of the porous copper body 110 can be set to be 0.025 mass% or less.
In the method for manufacturing the porous copper composite part 100 according to this embodiment, the copper fibers are laminated on the surface of the copper plate 120 made of copper or a copper alloy, and the sintering step S102 and the bonding step S103 are simultaneously performed. Therefore, it is possible to simplify the manufacturing process.
Hereinbefore, the embodiments of the present invention were described. However, the present invention is not limited thereto and can be appropriately modified in a range not departing from the technical idea of the invention.
For example, although the embodiments are described such that the porous copper body is manufactured using a manufacturing facility shown in FIG. 3, there is no limitation thereto and the porous copper body can be manufactured using another manufacturing facility.
The atmosphere of the oxidation treatment steps S21 and S121 has only to be an oxidation atmosphere in which copper or a copper alloy is oxidized at a predetermined temperature. Specifically, the atmosphere is not limited to the air atmosphere, and has only to be an atmosphere in which 10 vol% or greater of oxygen is contained in an inert gas (for example, nitrogen). The atmosphere of the reduction treatment steps S22 and S122 has only to be a reduction atmosphere in which a copper oxide is reduced into metal copper or the copper oxide is decomposed at a predetermined temperature. Specifically, it is possible to suitably use a nitrogen-hydrogen mixed gas or an argon-hydrogen mixed gas which contains several vol% or greater of hydrogen, a pure hydrogen gas, or an ammonia decomposed gas or a propane decomposed gas which is industrially used in many cases, and the like.
In addition, although the embodiments are described such that copper fibers made of tough pitch copper (JIS C1100) or oxygen-free copper (JIS C1020) are used, there is no limitation thereto and as a material of the copper fibers 11, it is possible to suitably use phosphorus deoxidized copper (JIS C1201, C1220), silver-containing copper (for example, Cu-0.02 to 0.5 mass% of Ag), chromium copper (for example, Cu-0.02 to 1.0 mass% of Cr), zirconium copper (for example, Cu-0.02 to 1.0 mass% ofZr), tin-containing copper (for example, Cu-0.1 to 1.0 mass% of Sn), and the like. Particularly, in a case of being used in a high-temperature environment of 200°C or higher, it is preferable to use the silver-containing copper, the chromium copper, the tin-containing copper, the zirconium-containing copper and the like, which are excellent in high-temperature strength.
Although the embodiments are described such that the skeleton of the porous copper body is formed by sintering the copper fibers, there is no limitation thereto and it is possible to set the oxygen concentration of the entirety of the skeleton to be 0.025 mass% or less by using a porous copper body such as fiber non-woven fabric and a metal filter having the oxygen concentration of 0.03 mass% or less, or by using a porous copper body as a raw material such as fiber non-woven fabric and a metal filter in which the oxygen concentration is decreased to 0.03 mass% or less by performing the preliminary reduction treatment S00, and the same effect is expected.
In the second embodiment, although the porous copper composite part having a structure shown in FIG. 4 is described as an example, there is no limitation thereto and a porous copper composite part having a structure as shown in FIG. 6 to FIG. 11 may be employed.
For example, as shown in FIG. 6, a porous copper composite part 200 in which a plurality of copper tubes 220 as a main body of the composite part are inserted into a porous copper body 210, may be employed.
Alternatively, as shown in FIG. 7, a porous copper composite part 300 in which a copper tube 320 as a main body of the composite part curved in a U-shape is inserted into a porous copper body 310, may be employed.
As shown in FIG. 8, a porous copper composite part 400 in which a porous copper body 410 is bonded to an inner peripheral surface of a copper tube 420 as a main body of the composite part, may be employed.
As shown in FIG. 9, a porous copper composite part 500 in which a porous copper body 510 is bonded to an outer peripheral surface of a copper tube 520 as a main body of the composite part, may be employed.
As shown in FIG. 10, a porous copper composite part 600 in which porous copper bodies 610 are bonded to an inner peripheral surface and an outer peripheral surface of a copper tube 620 as a main body of the composite part, may be employed.
As shown in FIG. 11, a porous copper composite part 700 in which porous copper bodies 710 are bonded to both surfaces of a copper plate 720 as a main body of the composite part, may be employed.

EXAMPLES

Hereinafter, results of a confirmation experiment carried out to confirm the effect of the present invention will be described.
Porous copper bodies including a skeleton with a three-dimensional network structure was manufactured using raw materials shown in Table 1.
An oxidation-reduction treatment was performed under conditions shown in Table 2 so as to manufacture porous copper bodies having 30 mm of width x 200 mm of length × 5 mm of thickness. In Inventive Examples 3 to 7, 9, and 10, a preliminary reduction treatment step was performed under conditions shown in Table 2.
Regarding each of the obtained porous copper bodies, oxygen concentration, porosity, and relative electrical conductivity thereof were evaluated. Evaluation results are shown in Table 3. An evaluation method will be described below.

(Fiber Diameter R)

As the fiber diameter R, an average value of an equivalent circle diameter (Heywood diameter) R=(A/π)^1/2×2, which was calculated through image analysis on the basis of JIS Z 8827-1 using a particle analyzer "Morphologi G3" manufactured by Malvern Instruments Ltd., was used.

(Fiber Length L)

As the fiber length L of the copper fibers, a simple average value, which was calculated through image analysis using the particle analyzer "Morphologi G3" manufactured by Malvern Instruments Ltd., was used.

(Oxygen Concentration of Fiber)

Approximately 1 g of copper fiber was put into a gas analyzer (model number: TCEN-600) manufactured by LECO CORPORATION, and an oxygen concentration (mass%) in the copper fiber was measured by an inert gas fusion method where a helium gas was used as a carrier gas.

(Oxygen Concentration C_O of Porous Copper Body)

Approximately 1 g of a sample was cut out from the obtained porous copper body and was put into the gas analyzer (model number: TCEN-600) manufactured by LECO CORPORATION, and then the oxygen concentration C_O (mass%) was measured by the inert gas fusion method where a helium gas was used as a carrier gas.

(Apparent Density Ratio D_A/D_T, and Porosity P)

A mass M (g) and a volume V (cm³) of the obtained porous copper body, and a true density D_T (g/cm³) of the copper fibers constituting the porous copper body were measured, and the apparent density Ratio D_A/D_T, and the porosity P(%) were calculated using the following expressions. The true density D_T was measured by an under-water method using a precision balance. $D_{A} / D_{T} = M / (V \times D_{T})$
$P = (1 - (M / (V \times D_{T}))) \times 100$

(Relative Electrical Conductivity C_R)

A sample having 10 mm of width × 500 mm of length × 5 mm of thickness was cut out from the obtained porous copper body, and electrical conductivity C₁ (S/m) was measured by a four terminal method on the basis of JIS C2525. The relative electrical conductivity C_R (%) was obtained based on electrical conductivity C₂ (S/m) of a bulk material which constitutes the porous copper body and is made of copper or a copper alloy, and the apparent density ratio D_A/D_T of the porous copper body using the following expression.

C_{R} (%) = C_{1} / (C_{2} \times (D_{A} \times D_{T})) \times 100

[Table 1]

		Copper fiber
		Material	Fiber diameter R (mm)	L/R	Oxygen concentration (mass%)
Inventive Examples	1	C1020	0.10	50	0.002
	2	C1020	0.05	250	0.002
	3	C1020	0.10	150	0.002
	4	C1020	0.10	25	0.002
	5	C1100	0.02	500	0.04
	6	C1100	0.10	60	0.04
	7	C1100	0.80	15	0.04
	8	C1220	0.20	35	0.01
	9	C1220	0.20	120	0.01
	10	C1441	0.08	50	0.01
Comparative Examples	1	C1020	0.10	80	0.002
Comparative Examples	2	C1020	0.10	80	0.002

[Table 2]

		Manufacturing process
		Preliminary reduction treatment step			Oxidation treatment step			Reduction treatment step
		Atmosphere	Temperature (°C)	Time (min)	Atmosphere	Temperature (°C)	Time (min)	Atmosphere	Temperature (°C)	Time (min)
Inventive Examples	1	-	-	-	Air	750	150	N₂-3%H₂	750	90
	2	-	-	-	Air	700	60	N₂-3%H₂	700	60
	3	N₂-3%H₂	500	90	Air	820	30	N₂-3%H₂	950	90
	4	Ar-10%H₂	850	5	Air	620	60	N₂-3%H₂	620	270
	5	N₂-3%H₂	650	100	Air	570	240	N₂-3%H₂	900	90
	6	N₂-3%H₂	750	10	Air	630	60	N₂-3%H₂	800	90
	7	100%H₂	400	120	Air	850	10	N₂-3%H₂	1080	10
	8	-	-	-	Air	780	30	Ar-10%H₂	1000	180
	9	Ar-10%H₂	800	60	Air	800	60	Ar-10%H₂	900	90
	10	N₂-3%H₂	750	100	Air	680	90	Ar-10%H₂	950	60
Comparative Examples	1	-	-	-	-	-	-	N₂-3%H₂	800	30
Comparative Examples	2	-	-	-	Air	950	60	-	-	-

[Table 3]

		Porous copper body
		Oxygen concentration (mass%)	Porosity (%)	Relative electrical conductivity (%)
Inventive Examples	1	0.002	71	30.3
	2	0.002	82	26.4
	3	0.002	64	45.2
	4	0.002	87	36.7
	5	0.012	78	22.5
	6	0.022	73	17.4
	7	0.015	53	19.9
	8	0.007	65	28.4
	9	0.008	70	24.5
	10	0.005	74	21.8
Comparative Examples	1	0.002	67	8.6
Comparative Examples	2	0.060	68	3.5

In Comparative Examples 1 and 2 in which the oxygen concentration of the entirety of the porous copper body was greater than 0.025 mass%, the relative electrical conductivity was less than 10%.
In contrast, in Inventive Examples 1 to 10 in which the oxygen concentration of the entirety of the porous copper body was set to be 0.025 mass% or less, the relative electrical conductivity was sufficiently high.
As described above, it was confirmed that it is possible to provide a porous copper body excellent in thermal conductivity and electrical conductivity according to the Inventive Examples.

INDUSTRIAL APPLICABILITY

It is possible to provide a porous copper body with particularly excellent thermal conductivity and electrical conductivity, a porous copper composite part in which the porous copper body is bonded to a main body of the composite part, a method for manufacturing the porous copper body, and method for manufacturing the porous copper composite part. For example, the present invention is applicable to electrodes and current collectors in various batteries, heat exchanger components, silencing members, filters, impact-absorbing members, and the like.

REFERENCE SIGNS LIST

10, 110: Porous copper body
11: Copper fiber
12: Skeleton
100: Porous copper composite part
120: Copper plate (Main body of the composite part)

Claims

A porous copper body, comprising:
a skeleton having a three-dimensional network structure,

wherein an oxidation-reduction layer formed by an oxidation-reduction treatment is provided on a surface of the skeleton, and

an oxygen concentration of an entirety of the skeleton is set to be 0.025 mass% or less.
The porous copper body according to Claim 1,
wherein a specific surface area of an entirety of the porous copper body is set to be 0.01 m²/g or greater, and a porosity of the entirety of the porous copper body is set to be in a range of 50% to 90%.
The porous copper body according to Claim 1 or 2,
wherein the skeleton is constituted by a sintered body made of a plurality of copper fibers, and in each of the copper fibers, a diameter R is set to be in a range of 0.02 mm to 1.0 mm, and a ratio L/R of a length L to the diameter R is set to be in a range of 4 to 2500.
A porous copper composite part, comprising:
a main body of the composite part; and

the porous copper body according to any one of Claims 1 to 3 bonded to the main body of the composite part.
The porous copper composite part according to Claim 4,
wherein a bonding surface of the main body of the composite part, to which the porous copper body is bonded, is made of copper or a copper alloy, and the porous copper body and the main body of the composite part are bonded to each other through sintering.
A method for manufacturing the porous copper body according to any one of Claims 1 to 3, comprising:
a skeleton forming step of forming the skeleton having the oxygen concentration of 0.025 mass% or less; and

an oxidation-reduction step of forming the oxidation-reduction layer on the surface of the skeleton.
The method for manufacturing the porous copper body according to Claim 6, further comprising:
a copper raw material lamination step of laminating a copper raw material having an oxygen concentration of 0.03 mass% or less; and

a sintering step of sintering a plurality of the copper raw materials which are laminated,

wherein in the sintering step, the copper fibers are oxidized and then the oxidized copper fibers are reduced, thereby bonding the copper fibers to each other so as to form the skeleton and forming the oxidation-reduction layer on the surface of the skeleton.
The method for manufacturing the porous copper body according to Claim 7, further comprising:
a preliminary reduction treatment of decreasing the oxygen concentration of the copper raw materials.
A method of for manufacturing a porous copper composite part which comprises: a main body of the composite part; and a porous copper body bonded to the main body of the composite part, comprising:
a bonding step of bonding the porous copper body manufactured by the method for manufacturing the porous copper body according to any one of claims 6 to 8, and the main body of the composite part to each other.
The method for manufacturing a porous copper composite part according to Claim 9,
wherein a bonding surface of the main body of the composite part, to which the porous copper body is bonded, is made of copper or a copper alloy, and the porous copper body and the main body of the composite part are bonded to each other through sintering.